In order to increase the cooling capacity of a convector lowering the delivery temperature of the process fluid even below the temperature of the ambient air, it is common practice to spray the tube bundle thereof with nebulized water which, evaporating into the air flow of the fan, lowers the temperature of said air flow and therefore also the temperature of the process fluid. Nonetheless, the water that evaporates leaves, on the tube bundle and on the fins thereof, deposits of the salts contained therein, e.g. lime and others. The accumulation of salts in the long term causes a reduction in the heat exchange capacity of the convector and thus makes it necessary to perform costly maintenance thereon and/or prior demineralization of the water to be nebulized resulting in increased costs. Existing systems are always provided with a plant for recirculation of the nebulized water, which has not yet evaporated, with a respective bleed valve to maintain the concentration of salts at acceptable levels.